Thread: Engine Valve as Chuck Backstop

Hi BT,
Sure looks like a winner to me except for three things.
1. I assume you'll have to face the front of the valve?or do they already run true?
2. How much do the stick out of the collet?(would spinning at top speed be a problem you think?)
3. Is something I've read about but never been is a position that it was an issue. How far does the collet pull back as you tighten it?

Stuart

That's nice Bob simple and effective

Nice one Bob
I guess you will turn down some for smaller dia work?
Do you find they move back a bit when you do the collet up?
Its just one more thing to add to the bottom of the list!

I guess there has to be some slight inward movement on tightening the collet but I'll have to obtain a new collet to let you know how much. That POS collet isn't worth refitting. As far as facing the valve goes, I haven't tried. Lou Cotter, the bloke who gave them to me has but he doesn't mind a shower of sparks when he does a bit of turning. He says they are hard. I ran an indicator on the valve face when the POS collet was pulled up tight, real tight to overcome the wobble. 0.0005" run out. Ok if you are making washers.

Stu, the answer to Question 2 is the depth of the chuck. in the case of the TOS, about 60 mm from the collet nose to the front of the newly modified jaws ( see Screwcutting to distraction for clarity ). The straight shank of the stem is 75mm long. I don't think speed would be an issue unless the valve you acquired was bent. These valves all ran true when held in the chuck and not that collet.

Ewan, if I was needing something smaller in diameter I could simply use a rod in a larger diameter collet. The 6, 10 and 12mm collets I have are of different manufacture and at worst, have 1/2 a thou run out.

BT

Hi Anorak Bob, Re. run out: Depending on how much work the valves have seen there might be some wear on the stem, generally it's toward the head end of the valve. You've probably measured the stem all along(where it runs in the valve guide) anyway but just thought I'd mention it. To state the obvious even a good collet won't like a worn stem.

Cheers.

Originally Posted by Log

Hi Anorak Bob, Re. run out: Depending on how much work the valves have seen there might be some wear on the stem, generally it's toward the head end of the valve. You've probably measured the stem all along(where it runs in the valve guide) anyway but just thought I'd mention it. To state the obvious even a good collet won't like a worn stem.

Cheers.

Log,

Assumption is always a good way of coming unstuck so I took heed and just measured the stems. Maybe a tenth of a thou variation along the length of the most worn valve. If the valves came out of one of Lou's motors I imagine the actual running time of the valves would be no more than a few minutes. He won his titles in the early nineties. 8.14 second ET was his best time if my poor memory serves me well enough.

The collet has a tight spot at the rear of the 5mm bore. The stems rock on that spot.

Bob.

Hi Bob,
I know you like making your own stuff, but if it all gets too hard Aloris make a chuck back stop. Not cheap tho

http://www.aloris.com/catalog/aloris_p46.pdf

Chris

Originally Posted by jack620

Hi Bob,
I know you like making your own stuff, but if it all gets too hard Aloris make a chuck back stop. Not cheap tho

http://www.aloris.com/catalog/aloris_p46.pdf

Chris

Chris,

From what I can glean looking at the Aloris images, it appears that the entire assembly is moved into position in the spindle bore then locked. Doesn't look like there is provision for fine adjustment.

I paid 19 bucks for a 5mm collet from Rotagrip. It, along with one of the valves, should provide a rough and ready stop. I'm thinking Bruce's 3C collet set up would be the simplest means of providing easy adjustablity without going to the trouble of making a purpose made back stop.

Bob.

Bob,
With the Aloris I think you put the workpiece where you want it in the chuck then bring the stop up behind it and lock it in place. I assume it's designed for multiple runs where you want many parts of the same thickness. I guess if you want to make very fine adjustments as you go it wouldn't be ideal. I can't see how your design allows for fine adjustment either though? For my 260 I've been thinking of a MT4 blank with a finely tapped hole to take threaded stops of a similar shape to your engine valves. Like many of my ideas it's unrefined and a long way down the list!

Anyway, I like your price better than the Aloris.

Originally Posted by jack620

Bob,
With the Aloris I think you put the workpiece where you want it in the chuck then bring the stop up behind it and lock it in place. I assume it's designed for multiple runs where you want many parts of the same thickness. I guess if you want to make very fine adjustments as you go it wouldn't be ideal. I can't see how your design allows for fine adjustment either though? For my 260 I've been thinking of a MT4 blank with a finely tapped hole to take threaded stops of a similar shape to your engine valves. Like many of my ideas it's unrefined and a long way down the list!

Anyway, I like your price better than the Aloris.

Adjustment would be a pain in the neck with the collet and valve set up Chris. The tailstock quill could be used to position the valve inwards but the only way to push the valve out, away from the spindle nose, is to remove the draw bar and push from the rear. Then the collet becomes loose.

I had all this covered when I made, or nearly made, this back stop. - https://www.woodworkforums.com/f65/la...ml#post1310953

Bob.

ps. I just read my initial post again. It is amazing how often after proof reading something still slips through. Competition. Not competion. Sorry.